Again, RAW is that you only roll for an ability check if the outcome is in doubt. There's no amount of help that will let me see the unknown better. You can't do it, so no roll because no doubt. The advantage roll never happens.
How are you making my vision better in the dark? What kind of help other than making light can you give to help me see the unknown to both of us?
That's why I said in the context of this discussion. This discussion is about seeing better on watch or in dim light where nobody has actually seen the thing in question. There's no one to help by pointing things out.
Yes, that is possible.
In low-light conditions, you would visually be looking for details that can still be seen in low-light conditions.
For example, when I was a kid and would go hunting with my dad early in the morning, I was taught (and learned) to pick out the general shape and outline of a deer -rather than relying on details such as color and other such things that you might look for in better visibility.
Similarly, later in life, when in the military, that same concept could be applied when standing watch as part of a security perimeter for a squad and/or when trying to seek out and close with enemy combatants in conditions of limited visibility. Such conditions included things like fog, sandstorms, and dim light.
On top of that, a more generalized Perception check would also include your other senses. Maybe you hear breathing or catch a scent of perfume.
Is it difficult? Yes, it is -hence the disadvantage to do it unaided.
With a trained combat squad such as group of delvers, teaming up in battle-buddy pairs to help mitigate some of that difficulty is possible.
Darkvision may not be quite as good as contemporary modern warfare gear, but it does allow being able to see without light. A party with Darkvision is neither blind nor incapable of seeing.